diff --git a/Library/MeasureCalc.cpp b/Library/MeasureCalc.cpp
index 092f6d44..f8248241 100644
--- a/Library/MeasureCalc.cpp
+++ b/Library/MeasureCalc.cpp
@@ -28,6 +28,7 @@ bool CMeasureCalc::c_RandSeeded = false;
 **
 */
 CMeasureCalc::CMeasureCalc(CMeterWindow* meterWindow, const WCHAR* name) : CMeasure(meterWindow, name),
+	m_ValidFormula(false),
 	m_LowBound(),
 	m_HighBound(100),
 	m_UpdateRandom(false)
@@ -57,10 +58,14 @@ bool CMeasureCalc::Update()
 {
 	if (!CMeasure::PreUpdate()) return false;
 
-	const WCHAR* errMsg = MathParser::Parse(m_Formula.c_str(), this, &m_Value);
-	if (errMsg != NULL)
+	if (m_ValidFormula)
 	{
-		LogWithArgs(LOG_ERROR, L"Calc: %s in [%s]", errMsg, m_Name.c_str());
+		const WCHAR* errMsg = MathParser::Parse(m_Formula.c_str(), this, &m_Value);
+		if (errMsg != NULL)
+		{
+			LogWithArgs(LOG_ERROR, L"Calc: %s in [%s]", errMsg, m_Name.c_str());
+			m_ValidFormula = false;
+		}
 	}
 
 	return PostUpdate();
@@ -101,7 +106,11 @@ void CMeasureCalc::ReadConfig(CConfigParser& parser, const WCHAR* section)
 		if (errMsg != NULL)
 		{
 			LogWithArgs(LOG_ERROR, L"Calc: %s in [%s]", errMsg, m_Name.c_str());
-			m_Formula.clear();
+			m_ValidFormula = false;
+		}
+		else
+		{
+			m_ValidFormula = true;
 		}
 	}
 }